1. Field of the Invention
The present invention relates to a gas insulated switch gear device and, in particular, relates to a delay mechanism in an actuating device for a gas insulated switch gear device which performs a delay operation delayed by a predetermined time difference.
2. Conventional Art
A circuit breaker using an insulating gas (hereinafter called a gas circuit breaker) is generally constituted by a plurality of circuit breaking contacts inserted in series in a main circuit to thereby interrupt a current flowing through the main circuit. Currently, a plan of power transmission lines having a line voltage of 1000 kV has been materialized, and in view of such structural limitations as earthquake resistance and cost reduction, the height of power transmission line towers is reduced as much as possible. Accordingly, it is required to suppress an overvoltage level generated during current interruption by a circuit breaker. For this purpose, a so-called resistance circuit breaking system has being employed in which a resistor body is inserted in the main circuit after interruption of a main circuit breaking portion, and the current transferred to the resistor body is then interrupted by the resistance circuit breaking portion connected in series with the resistor body.
For realizing such a system, it is necessary for the resistance circuit breaking portion to be opened after opening of the main circuit breaking portion with a predetermined time difference. Many mechanisms for achieving such an opening time difference have been proposed. JP-B-2-50574(1990) and JP-B-2-22487(1990) disclose an example of such mechanisms wherein a coil spring is used as a driving source and the delay time is obtained from the time required for tensioning the spring and the delay of the spring operation time due to the inertia. In the instant example, the coil spring serving as the driving source for the resistance circuit breaking portion is disposed at a high voltage portion in a gas container; therefore, for an ordinary periodic inspection it has been necessary to recover and recharge gas in the container, which requires a long time. Further, constant monitoring of the driving source is difficult.
In order to improve such maintenance difficulties, a gas circuit breaker is proposed in which an actuating device for the main circuit breaking portion and for the resistance circuit breaking portion is disposed at a grounding potential portion. The gas circuit breaker is provided with a control mechanism such as a pilot valve which controls transmission of drive energy to an actuating piston, a first drive source for driving the main circuit breaking portion, a second drive source for driving the resistance circuit breaking portion which is designed to operate successive to the operation of the main circuit breaking portion, and a mechanical delay operation mechanism which actuates a pilot valve mechanism for the second drive source via an auxiliary link mechanism coupled to the actuating piston. However, with the mechanism which actuates the pilot valve for the resistance circuit breaking portion by the mechanical delay operation mechanism alone, when the operation of the delay operation mechanism malfunctions during tripping and the subsequent making operation of the gas circuit breaker, a required normal operation may not be obtained. Further, break-down or wear of the mechanical delay operation mechanism may cause the reliability of the expected operation to decrease.